1. Field of the Invention
This invention relates to a preservative composition which improves wood properties and to a process of treating wood with such a composition.
2. Description of the Prior Art
It has long been known that wood, if not properly treated and exposed to outdoor conditions over prolonged periods of time will tend to deteriorate. Such deterioration may be caused by rotting under the influence of moisture, insect attack, biological degradation or other means.
Various means have been developed to protect wood from deterioration. Simple surface treatment such as painting and/or impregnation of various preservatives into the wood have long been known.
Among the known types of wood preservatives are oily preservatives such as creosote or pentachlorophenol in heavy oil as well as water borne copper-chrome-arsenate preservatives as well as ammoniacal copper arsenate (ACA). See generally, Distribution and Effectiveness in Pinus Sp of a Water-Repellent Additive for Water Borne Wood Preservatives, Levi et al., Forest Products Journal, Vol. 20, No. 11, pp. 32-37 (Nov., 1970).
It has been known to treat wood with chromated copper arsenate (CCA) emulsions, including CCA-oil emulsions, in order to resist decay of the wood, insect attack and biological degradation of the same.
It has also been known to use such treatments in wood products, such as utility poles, which are intended for long term use in outdoor environments.
It has also been suggested to employ copper-chromearsenate treatment solutions having a self-dispersing additive which is said to consist of a hydrophobic constituent which is a blend of long-chain petroleum hydrocarbon fractions, a surface active agent which is said to be a blend of non-ionic surfactants, and a petroleum-distillate solvent. See "Emulsion Additives: A New Concept in Copper-Chrome-Arsenate Treatment" pp. 69-93.
It has also been known to suggest the use of nonylphenyl ethoxylates as in preservative compositions for wood. See United States Patent Application No. 713,386. See also GAF IGEPAL CO Nonionic Surfactants product literature.
U.S. Pat. No. 3,832,463 discloses a water in oil wood preservative employing hydrophobic wax. It also discloses the use of a non-ionic surface active agent having an HLB value between 7 and 11.
U.S. Pat. No. 4,313,976 discloses the use of a coloring agent in the form of an organic dye in a wood preservative material.
U.S. Pat. No. 3,378,381 discloses an emulsion for preserving and fireproofing wood. A non-reactive preservative (chlorinated phenol) is employed in the oil phase. It teaches the use of a quantity of oil equal to or greater than the amount of water in the emulsion. It discloses incorporating of preservatives in the aqueous phase, but provides an emulsion system which would tend to cause rapid and extensive sludge formation as the chromate and arsenate type materials would react with the lignin sulfonate surfactants which he discloses.
It has been known that chromated copper arsenate may be used beneficially in the preservation of wood through resisting decay, insect attack and other forms of biological degradation. While this material is environmentally safe, it has presented problems. It is known that highly charged anions and cations serve to break emulsions. As fresh aqueous solutions of chromated copper arsenate contain such ions as HCrO.sub.4.sup.-, CrO.sub.4.sup.2- Cu.sup.2+, H.sub.2 AsO.sub.4, HAsO.sub.4.sup.2- and AsO.sub.4.sup.3-. Emulsion of such ions will have poor stability. Also, the chromated copper arsenate solutions are highly acidic tending to have a pH in the range of about 1.8 to 2.2 and are oxidative in nature. As a result, emulsifiers which are unstable in acid or which can be readily oxidized may not be used with such solutions.
European Pat. No. 0043035 discloses a water in oil emulsion which employs pigments as colorants.
U.S. Patent Application Ser. No. 941,754 discloses a wood preservation system which includes bringing together under the influence of ultra high shear emulsifying water and oil phases wherein the emulsion has an emulsifying agent. One end of the emulsifying agent reacts with the oil while the other end reacts with the water. The emulsifying agents are said to be ethoxylated amines or fatty amines with ethoxylated diamines being preferred. The use of a rhelogy structuring agent which is a high mole ratio, water soluble polymer of ethylene oxide is also disclosed. Ultra high shear equipment is required in order to make this emulsion.
In spite of these prior art disclosures, there remains a very real and substantial need for an effective wood preservative composition which will provide a wide variety of desirable properties for the wood while being storage stable and, more specifically, there is need for such a composition which contain chromated copper arsenate and an oil emulsion.